Every place I've ever worked, the policy was that occurrence reports were separate from the client's medical record and the existence of the report was not mentioned in the medical record. However, it doesn't really make a whole lot of difference -- if there's going to be a lawsuit, attorneys know that an occurrence report was probably generated, they subpoena it, and they get it. I worked as a hospital surveyor for my state and the Feds for several years, and we would routinely request the occurrence reports when we were investigating complaints or other "bad outcome" situations, and the hospitals would just hand them to us (occasionally, one hospital or another would balk, but we'd just point out that we'd get them in the end, anyway, so they might as well just give them to us). If we were looking for a pattern of something occurring over time, we'd ask for ALL the occurrence reports from X date to the present, and they'd just hand us the whole stack.
So, long story short, there's always been this big mystique about the occurrence reports and keeping them secret, but, in real life, it just doesn't make much difference -- the outcome is going to be the same in any case.